Answer & Explanation
B) 1957 April
India switched from the rupee, pie system to decimal currency on 1 April 1957. The decimalisation of currencies is the process of converting each country's currency from its previous non-decimal denominations to a decimal system, with one basic unit of currency and one or more sub-units, such that the number of sub-units in one basic unit is a power of 10, most commonly 100).
In India, Pakistan, and other places where a system of 1 rupee = 16 annas = 64 paise = 192 pies was used, the decimalisation process defines 1 naya paisa = 1⁄100 rupee.